Urban Vulnerability to Terror – A Different Look

There has been an ongoing debate among politicians and practitioners about the apportionment of funding for urban security to combat terrorism. Not unexpectedly, those from the targets of September 11th, New York City and Washington DC, argue that their cities remain at the highest threat. Perhaps that is so. Contrary arguments have come from many smaller areas, some in rural sections of the country claiming that remotely located chemical plants represented significant targets. Similarly, I am aware of one Appalachian location in which a system of dams, if breached by a terrorist attack might impact a number of larger cities down stream.

A recently published study, yielded surprising results, including finding Boise, the capital of Idaho in the top 10 most vulnerable cities in the country, and the only Western city in that group. The study funded by the Department of Homeland Security was based on a unique (actually complex) mathematical calculation. The study, which originally appeared in the December Journal of Risk Analysis, factors not only the risk of terrorist attacks, but also social demographics, natural hazards (floods, wildfires, earthquakes, extreme weather, etc.) and infrastructure vulnerability (roads, bridges, tunnels, ports, dams, skyscrapers, etc.). The result is an index of an area’s vulnerability to hazards. This is often referred to as an “all hazards” approach to emergency response.

Within an “all hazards” framework, the vulnerability of an urban area’s social systems and built environment exists independent of an adverse event. Thus, we can understand the underlying characteristics that contribute to such vulnerability and then relate these characteristics to likely impacts, be they from natural, technological, or human-induced threats such as terrorism.

While the statistical basis and analytical method is beyond my skill set, its clear that an “all hazards” approach to city or regional vulnerability provides sometimes unexpected results. For reference, a good example of an all hazards regional group is found in the Maryland All Hazards Consortium.

So, why is Boise, Idaho in the top 10 most vulnerable U.S. cities (according to this study)?

Boise, it seems, faces high risk from extreme events such as wildfires or failure of a large dam upstream, Piegorsch said. Seventeen miles northeast of Boise, Lucky Peak Dam extends 2,340 feet long and 340 feet high. The 12-mile-long reservoir behind it stores 300,000 acre-feet of water.

As with any other attempt to do statistical and predictability analysis of an unknown event, there are critics, including those who question whether this type of information should be public. However, Henry Willis who is a researcher at the Rand Corporation and a co-author of a study on terrorism risk modeling commented that “Studying vulnerability is an important part of understanding risk.” He also called the study "a novel way of thinking about the vulnerability of cities."

"They developed a measure of vulnerability that goes beyond what people have used in the past," he said.
"The study suggests they have some ability to predict where events with catastrophic consequences will occur. The question is, are they measuring the right components? Have they identified the full set of components, and what are they missing?"

Clearly, risk is higher is areas of denser population. However, examination of the list might surprise some people. For example, Knoxville Tennessee, a city with a population of less than 200,000 is on the list (while the larger MSA has nearly 650,000 people, it is probably on the list because of its proximity to Oak Ridge National Laboratory). Certainly, for a study of risk vulnerability to be truly relevent, it also needs to be flexible to reflect changes in an area’s risk profile. As a simple example, of the five cities now under consideration as a location for the new DHS National Bio Agro Defense Facility, only two are on the current list.